In order to understand the mechanism by which epithelial cells recognize, and attach and spread on their complementary basement membrane, we aree using the hydra mesoglea as a model system. The mesoglea represents one of the earliest evolved basement membranes, and it serves to hold the epithelial cells of this tissue level organism together. Using our method for purifying intact mesogleas from hydra and another method for preparing suspensions of hydra epithelial cells, we show that these cells recognize, and attach and spread only on the isolated mesoglea. Our aim is to isolate, and characterize those components within the matrix of the mesoglea (hydra basement membrane) as well as those within the epithelial cells which are involved in these recognition and attachment processes. Because most human tumors arise within epitheliallayers (carcinoma), an understanding of normal and abnormal attachment of epithelial cells should prove valuable. Furthermore, basement membranes are considered to affect embryonic development and differentiation, as well as the maintenance and repair of tissues in both the normal or pathological states as that occurring in wound healing or burned tissue repair.